KR101003177B1 - Preparation of organic coated inorganic nanoparticles using block-copolymers - Google Patents

Abstract

The present invention chemically bonds a poly (styrene- b -vinylbenzylchloride) block copolymer to the surface of an inorganic nanoparticle through a reaction, and treats the block copolymer by treating the incomplete inorganic nanoparticle-polymer composite having a polymer layer with an amine. The present invention relates to a method for preparing an inorganic nanoparticle-polymer composite having a block having a vinylbenzyl ammonium salt formed therein to form an inner layer and a surface treated such that a polystyrene block forms an outer layer.

Inorganic nanoparticles, block copolymer, dispersion, nanocomposite, coating

Description

Preparation method of inorganic nanoparticles coated with organic polymer using block copolymers {Preparation of organic coated inorganic nanoparticles using block-copolymers}

In the present invention, the block copolymer is used as a coating material, and the chemical bonding, polarity, and electrostatic properties are changed on the surface of the inorganic nanoparticles. The present invention relates to a method for preparing inorganic nanoparticles having an organic polymer coating layer having a thick and dense coating density.

In general, organic surface treatment of inorganic nanoparticles is performed for various purposes and forms. In the case where the inorganic nanoparticles are treated with the nonpolar organic layer, the dispersibility of the particles in the nonpolar medium is increased to enable the treatment with the homogeneous dispersion solution. This function forms a polymer-inorganic particle nanocomposite especially when the dispersion medium is a polymer, and plays a very important role in improving polymer properties, and is applied to various materials such as high strength structural materials, high barrier films, and various functional films. In addition, it plays a role of minimizing the chemical and physical denaturation of the particles from external environmental factors, and may change the physical properties of the particles themselves according to the surface adhesion component. The organic surface treatment of inorganic particles exhibiting such action is a method of attaching to the surface by chemical bonding using functional groups of monomolecular substances, an attachment method by physical adsorption such as electrostatic interaction using functional groups of monomolecular substances, polymer The entanglement of the materials is formed on the surface of the particle and coated, the functional group of the polymer chain forms a chemical bond with the surface of the particle, or the coating method by physical adsorption by electrostatic interaction.

According to the surface treatment method of the inorganic particles, the appearance and properties of the coating appear to be different. In general, surface treatment using a monomolecular material forms an organic surface layer composed of one molecular layer, and the thickness thereof is about 1 to 2 nanometers at a few millimeters. In this case, it can be said that it is difficult to increase the surface thickness or increase the stability of the organic surface layer. In the case of coating the surface with a polymer material, the adhesion by the electrostatic interaction can form a coating layer having a relatively uniform thickness by a simple process, but may be easily removed and detached due to the external environment change such as the solvent or the polymer matrix. The coating in which the polymer chains are simply entangled on the particle surface is difficult to obtain a stable coating layer of uniform thickness.

The present invention provides a method for producing inorganic nanoparticles coated with organic polymer, stable to changes in external solvents and media, uniform thickness of the coating layer and to exhibit sufficient organic surface properties at the level of several nanometers, The high dispersibility in the medium is intended to be sufficient for application to polymer-inorganic nanocomposites.

The present invention,

Reacting the surface of the inorganic nanoparticles with poly (styrene- b -vinylbenzylchloride) which is a block copolymer; And

The second step of forming a double layer of a vinyl benzyl ammonium salt block and a polystyrene block on the surface of the inorganic nanoparticles by adding an amine to the first step reactant

There is a feature in the method for producing an inorganic nanoparticles coated with an organic polymer comprising a.

The organic coating inorganic nanoparticles prepared by the method proposed in the present invention has a block copolymer coating layer formed through a two-step reaction, and the coating layer has an inner layer strongly attached to the surface by electrostatic action and polar interaction, and a polymer. Since the chains have a double layer structure having a nonpolar polymer layer interacting freely with a nonpolar organic solvent or a medium as an outer layer, inorganic particles can be effectively dispersed in a nonpolar solvent or a polymer matrix. In addition, this coating layer is formed by a two-step process, and its formation density is the same as that of bulk polystyrene, which is the highest density organic coating layer that can be obtained by surface treatment, and the organic material is attached to the sparse surface at low density. It has high barrier properties and stability which is difficult to obtain in other surface treatment methods. As a result, the surface organic layer is stably formed even after drying, and the organic coating layer is stably maintained even after repeated washing of the particles with an organic solvent. The organic coating layer formed by the method proposed in the present invention exhibits a thickness of 3 to 7 nm and exhibits a coating thickness sufficient to serve as a binder for attaching inorganic particles to each other even in the absence of a medium, but agglomeration of particles in the coating process. The phenomenon does not appear. The method for preparing inorganic nanoparticles coated with organic polymers presented in the present invention exhibiting the above characteristics is useful as inorganic particles for inorganic additives of various thin films and films prepared by improving polymer properties and nanodispersion materials and solution processes. It is expected.

The present invention chemically bonds a poly (styrene- b -vinylbenzylchloride) block copolymer to the surface of an inorganic nanoparticle through a reaction, and treats the block copolymer by treating the incomplete inorganic nanoparticle-polymer composite having a polymer layer with an amine. The present invention relates to a method for preparing an inorganic nanoparticle-polymer composite having a block having a vinylbenzyl ammonium salt formed therein to form an inner layer and a surface treated such that a polystyrene block forms an outer layer.

The two block portions of the block copolymer used in the present invention are responsible for their respective functions during surface coating of the inorganic nanoparticles. One block part serves to maintain and maintain dispersion through nonpolar interaction with a solvent or polymer matrix, and forms an outermost organic layer of the coating. The other part contains functional groups such as alkyl halides to chemically bond with reactive groups on the surface of inorganic particles such as metal oxy anions. In addition, it forms an ammonium salt in the reaction with the amine, changing its properties from nonpolar to polar blocks, and serves as an inner layer of the coating through electrostatic and polar interactions with the surface of the inorganic nanoparticles.

The process of dividing the organic coating layer into two stages is because each step process is important to form a high density organic coating layer which is finally stable and has a thickness of several nanometers. In the step where the chemical bond is formed between the block copolymer and the inorganic nanoparticle surface in the first step, the block copolymer is first attached to the surface as a single layer. In this case, the block copolymer has a high density because the surface reactive groups are not high in density. It is difficult to attach and difficult to achieve stable and complete coating. In this state, the block copolymer polymer chains in the solution form an unstable secondary layer on the primary surface layer. However, they can easily be washed away by solution or aggregated together regardless of the core inorganic nanoparticles. In this two-step process of applying the amine compound in the surface state of the particles, the unstable block copolymer layer is transformed into a stable double organic coating layer through self-assembly at the surface of the particles in which two portions of the ammonium salt forming block and the nonpolar block are temporarily formed. do. In this change, the density of the organic layer is increased to the bulk polymer level and shows a uniform thickness of 3 to 7 nm.

Hereinafter, a method of manufacturing the inorganic nanoparticles coated with the organic polymer using the block copolymer according to the present invention will be described in detail.

First, the surface of the inorganic nanoparticles is treated with UV-ozone to form a hydroxyl group, and then reacted with a strong base with anhydrous conditions to form a metal oxy anion. Inorganic nanoparticles to be used are compounds represented by the following formula (1) and the particle size is used in the range of 3 ~ 200 nm.

M _m L _n O _l

In Formula 1, M is one or two or more typical metals selected from elements 1A to 4A of the periodic table, L is one or two or more metal elements selected from transition metals and lanthanide metals, and m is 0 to 4 An integer, n is an integer from 0 to 4, l represents an integer from 1 to 8, provided that m and n are not 0 at the same time.

Examples of the inorganic nanoparticles include BaTiO _{3 ,} TiO ₂ , SiO ₂ , Al ₂ O ₃ , V ₂ O ₃ , ZnO ₂ , La ₂ O ₃ , HfO ₂ , SrTiO _3, SrTiO _{3 ,} Nb ₂ O _{5 ,} and the like. Can be mentioned.

LiH, NaH, KH, CaH ₂ , alkyl lithium having 1 to 10 carbon atoms may be used as the strong base that reacts with the surface of the inorganic nanoparticles. The reaction with the strong base is carried out at room temperature under nitrogen or argon by dispersing the inorganic nanoparticles in anhydrous aprotic organic solvent. After the reaction, the particles having the oxy anion formed on the surface and the block copolymer are reacted in an organic solvent. The block copolymer uses poly (styrene- b -vinylbenzylchloride). In this case, the molecular weight of the styrene block and the vinyl benzyl chloride block is between 2000 and 50000, respectively, and the mole ratio of vinyl benzyl chloride to styrene is in the range of 0.1 to 80%. If the ratio exceeds 80%, the ratio of the non-polar part in the polymer layer to be finally formed is reduced, so that the dispersibility in the non-polar medium is reduced. The organic solvent used in the reaction is an anhydrous aprotic solvent which can completely dissolve the block copolymer homogeneously, but esters and alkyl halides which can react with strong bases are not used. Therefore, tetrahydrofuran, toluene, diphenyl ether and the like are used. The block copolymer layer formed around the inorganic particles after the reaction is incomplete and consists of a chemical bond attached to the surface and a layer enclosed thereon secondarily. The block copolymer layer may be formed in a weight ratio of up to 50% of inorganic nanoparticles, but gradually decreases to 1% in content ratio with washing. In this washing step, the content of the block copolymer layer remaining on the surface is adjusted to 10 to 50% by weight. Less than 10% by weight is insufficient in the polymer content to form the organic layer in the formation of the organic layer of the next step, in the case of 50% by weight or more to increase the aggregation of the polymer particles are formed separately regardless of the particle surface.

Next, the particles on which the organic layer is formed are reacted with the amine in a solution. The amines used are primary, secondary and tertiary alkyl amines, and the alkyl group may have a size of 1 to 20 carbon atoms. In this reaction step, the methyl chloride groups of the vinylbenzyl chloride block react with the amine to form an ammonium salt. The block portion in which the ammonium salt is produced while the block copolymers surround the surface of the particle interacts with the inorganic nanoparticle surface to form an inner layer and a styrene nonpolar block is formed thereon. When the formation of the organic layer is completed, the polymer organic layer which is stably formed even after washing and drying and is uniformly coated with a thickness of 3 to 7 nm can be directly observed with a transmission electron microscope.

In the above process, the inorganic nanoparticles coated with the organic layer may be manufactured in the present invention, and the particles are generally sufficiently dispersed in an organic solvent and a polymer matrix in which inorganic particles are difficult to stably be dispersed, and the dispersion state is maintained even after elapse of time. Shows the result. In this case, as the solvent used for the dispersion, chloroform, dichloromethane, dichloroethane, tetrachloromethane, toluene, benzene, tetrahydrofuran and the like can be used. In particular, hexane, heptane, octane, dodecane and the like can be used as the hydrocarbons having a very low polarity and are hard to be sufficiently dispersed from a general emulsifier or a polymer dispersant. Inorganic nanoparticles coated with an organic layer provided in the present invention can also be applied to polystyrene, polyethylene, polycarbonate, polyacrylate, etc. as a polymer matrix, and those polymer materials are dissolved in a solvent, dispersed and mixed, and dried, and each polymer material. In the monomer state of the mixed with the particles and then proceed with the polymerization to form a polymer matrix are all possible.

In addition, since the inorganic nanoparticles provided in the present invention form a stable polymer layer corresponding to several nanometers, in the absence of a solvent, these particles may exhibit binding properties to each other. The action of the organic layer formed of the double layer of the block copolymer can be well confirmed from the results showing the glass transition temperature inherent in polystyrene even after the inorganic nanoparticles are coated.

Inorganic nanoparticles prepared by the present invention has a coating thickness of 1 to 10 nm, preferably has a coating thickness of 3 to 7 nm.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by the following Examples.

Example 1

Barium titanate (BaTiO ₃ ), UV-ozone treated with 100 mL of tetrahydrofuran, 5 g of the average particle size 75 nm) and 0.5 g of sodium hydride are dispersed and stirred at room temperature under nitrogen for 8 hours. 50 mL of tetrahydrofuran dissolved in 10 g of poly (styrene- b -vinylbenzylchloride) having a molecular weight of 7000 and a polyvinylbenzylchloride block having a molecular weight of 7500 and a mole ratio of styrene to vinylbenzylchloride 3: 1 was reacted. To 80 ^° C, stirred for 24 hours to react. The surface treated particles are separated by centrifugation, washed with tetrahydrofuran and vacuum dried for 48 hours. 20 mL of triethylamine is added dropwise while stirring and dispersing the prepared particles in 100 mL of toluene and reacting with stirring at room temperature for 48 hours. Under reduced pressure, unreacted triethylamine and toluene were removed, washed and dried in vacuo.

The prepared particles were observed the thickness of the organic coating layer by transmission electron microscope, and the content of the organic material was quantified by thermal mass spectrometry. Table 1 shows the dispersibility by dispersing in toluene, tetrahydrofuran and octane solution.

Example 2

In the same manner as in Example 1, except that the polystyrene block has a molecular weight of 15000, the polyvinylbenzyl chloride block has a molecular weight of 12000, and the styrene-vinylbenzylchloride molar ratio of 3: 1 blocks poly (styrene- b -vinylbenzylchloride). Organically coated particles were prepared using the copolymer.

Example 3

In the same manner as in Example 1, organic coated particles were prepared using titanium oxide (average particle size 50 nm) particles instead of barium titanate particles.

Example  4

In the same manner as in Example 1, organic coated particles were prepared using silica (average particle size 55 nm) particles instead of barium titanate particles.

Comparative Example 1

In the same manner as in Example 1, styrene and vinyl benzyl chloride is randomly copolymerized in place of the poly (styrene- b -vinylbenzylchloride) block copolymer, the mole ratio of styrene and vinyl benzyl chloride is 4: 1 and the molecular weight is 14000. Organic coated particles were prepared using phosphorus poly (styrene- co -vinylbenzylchloride).

Comparative example  2

The same procedure as in Example 1 was carried out, but the particles were prepared by omitting the amine treatment part of the second step. That is, barium titanate (BaTiO ₃ , UV-ozone treated with 100 mL of tetrahydrofuran) 5 g of the average particle size) and 0.5 g of sodium hydride are dispersed and stirred at room temperature and under nitrogen for 8 hours. 50 mL of tetrahydrofuran dissolved in 10 g of poly (styrene- b -vinylbenzylchloride) having a molecular weight of 7000 and a polyvinylbenzylchloride block having a molecular weight of 7500 and a mole ratio of styrene to vinylbenzylchloride 3: 1 was reacted. And reacted by stirring at 80 ^o C for 24 hours. The surface treated particles are separated by centrifugation, washed with tetrahydrofuran and vacuum dried for 48 hours.

Comparative example  3

UV-ozone treated barium titanate (BaTiO ₃ , 100 mL toluene) 5 g of average particle size 75 nm) were dispersed, the polystyrene block had a molecular weight of 7000, the polyvinylbenzylchloride block had a molecular weight of 7500, and the mole ratio of styrene to vinylbenzylchloride was 3: 1 poly (styrene- b -vinylbenzylchloride) 10 50 mL of a solution of toluene dissolved therein was added to the reaction product, and 20 mL of triethylamine was added dropwise, followed by reaction at room temperature for 48 hours. The particles are separated by centrifugation and depressurized to remove unreacted triethylamine and toluene, washed and dried in vacuo.

Comparative example  4

Tetrahydrofuran solution 50 containing 5 g of UV-ozone treated barium titanate (BaTiO ₃ , average particle size 75 nm) in 100 mL of tetrahydrofuran, and dissolving 10 g of poly (vinylpyrrolidone) (molecular weight 22000). Add mL to the reaction and stir at room temperature for 48 hours. The particles are separated by centrifugation, washed and dried in vacuo.

Experimental Example  One

Experiments were performed to determine the dispersoids of the organic solvents of the particles prepared in Examples 1 to 4 and Comparative Examples 1 to 4. The prepared particles were dispersed in tetrahydrofuran, toluene and octane, and the size of the dispersed particles was confirmed by a dynamic light scattering device, and the organic polymer layer coated with a transmission electron microscope was confirmed.

Dispersibility for the polymer matrix was added to the styrene monomer and AIBN in 3wt% ratio, and then dispersed, and the polymerization proceeded with stirring at 100 ^° C. for 24 hours. The formed polymer matrix was made into thin sections, and the distribution of particles was confirmed by transmission electron microscope.

division Organic polymer weapon
particle coating
thickness Dispersibility
(Particle average R _H ) Tetrahydrofuran toluene octane polystyrene Example 1 Poly (styrene-b-vinylbenzylchloride)
Block copolymer
Molecular Weight 7000/7500 BaTiO ₃ 5 nm good
(110 nm) good
(120nm) good
(180 nm) good Example 2 Poly (styrene-b-vinylbenzylchloride)
Block copolymer
Molecular Weight 15000/12000 BaTiO ₃ 7 nm good
(108nm) good
(122nm) good
(150nm) good Example 3 Poly (styrene-b-vinylbenzylchloride)
Block copolymer
Molecular Weight 7000/7500 TiO ₂ 5 nm good
(70 nm) good
(88nm) good
(75nm) good Example 4 Poly (styrene-b-vinylbenzylchloride)
Block copolymer
Molecular Weight 7000/7500 SiO ₂ 4 nm good
(68 nm) good
(90nm) good
(127nm) good Comparative Example 1 Poly (styrene-co-vinylbenzylchloride)
Random copolymer
Molecular Weight 14000 BaTiO ₃ 3 nm good
(98nm) Sedimentation Sedimentation Bunch Comparative Example 2 Poly (styrene-b-vinylbenzylchloride)
Block copolymer
Molecular Weight 7000/7500
(Omitted ammonium) BaTiO ₃ - Poor dispersion
(Partial sedimentation) Sedimentation Sedimentation - Comparative Example 3 Poly (styrene-b-vinylbenzylchloride)
Block copolymer
Molecular Weight 7000/7500
(Omit surface reaction) BaTiO ₃ - Sedimentation Sedimentation Sedimentation - Comparative Example 4 Poly (vinylpyrrolidone)
Molecular Weight 22000 BaTiO ₃ - Dispersibility
Bad
(Partial sedimentation) Sedimentation Sedimentation Bunch

As shown in Table 1, the particles coated with the polymer organic layers of Examples 1 to 4 according to the present invention showed excellent dispersibility in the illustrated organic solvent and the polystyrene matrix. In addition to the barium titanate particles, such dispersibility was also observed without significant change in titanium oxide and silica particles. As illustrated in Example 2, the change in molecular weight of the block copolymer did not affect the dispersibility. The thickness of the coating layer confirmed through the transmission scanning electron microscope showed a uniform thickness in the range of 4 to 7 nm, and it was confirmed that the coating layer was maintained in a perfect form even after the treatment such as drying and washing the solution.

On the other hand, inorganic nano-molecules coated with organic polymers prepared by the same process using random copolymers instead of block copolymers have significantly reduced dispersibility, showing good dispersibility only in tetrahydrofuran, but not in octane and toluene. It could be confirmed that precipitation was not achieved and precipitation was formed. In addition, the polymer matrix also showed the results of agglomerated particles. In this case, the polymer coating layer exhibited a thickness of about 3 nm.

It was confirmed in the results of Comparative Examples 2 and 3 that each step of forming the coating layer of the block copolymer also plays an important role in the final coating layer properties. That is, if the surface reaction step of step 1 and the ammoniumation step of step 2 are omitted, the coating layer having a constant thickness cannot be observed due to insufficient coating, and the dispersibility to the organic solvent does not appear. Even coating with polyvinylpyrrolidone, which is a general polymer emulsifier, did not obtain a stable coating layer and dispersion effect.

From the above results, it can be seen that the organic polymer coating layer that is stable and excellent in dispersibility can be formed on the surface of the inorganic nanoparticles by the coating method consisting of 1,2 steps using the block copolymer.

1 is BaTiO ₃ coated with an organic polymer layer prepared in Example 1 according to the present invention Transmission electron micrograph of the particle.

Claims (9)

After the UV-ozone treatment, the first step of reacting the surface of the inorganic nanoparticles treated with a base selected from LiH, NaH, KH and alkyl lithium having 1 to 10 carbon atoms with poly (styrene- b -vinylbenzylchloride) as a block copolymer ; And The second step of forming a double layer of a vinyl benzyl ammonium salt block and a polystyrene block on the surface of the inorganic nanoparticles by adding an amine to the first step reactant Organic polymer coated inorganic nanoparticles manufacturing method characterized in that it comprises a. The method of claim 1, wherein the poly (styrene- b -vinylbenzylchloride) has a molecular weight of styrene blocks and vinylbenzylchloride blocks in the range of 2000 to 50000, respectively. The method of claim 1, wherein the poly (styrene- b -vinylbenzylchloride) has a molar ratio of vinylbenzylchloride to styrene in the range of 0.1 to 80%. The method according to claim 1, wherein the inorganic nanoparticles are compounds represented by the following Chemical Formula 1, wherein the inorganic nanoparticles are nanoparticles having a particle size in the range of 3 to 200 nm. [Formula 1] M _m L _n O _l In Formula 1, M is one or two or more typical metals selected from elements 1A to 4A of the periodic table, L is one or two or more metal elements selected from transition metals and lanthanide metals, and m is 0 to 4 An integer, n is an integer from 0 to 4, l represents an integer from 1 to 8, provided that m and n are not 0 at the same time. delete The method of claim 1, wherein the amine is selected from primary, secondary and tertiary alkylamines having 1 to 20 carbon atoms. The method of claim 1, further comprising a washing step of controlling the content of poly (styrene- b -vinylbenzylchloride) remaining on the surface of the inorganic nanoparticles after the step 1 to 10 to 50% by weight relative to the inorganic nanoparticles. Manufacturing method characterized in that. The method of claim 1, wherein the coating thickness of the organic polymer coated on the surface of the inorganic nanoparticles is in the range of 1 to 10 nm. delete

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